From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F3081C56202 for ; Wed, 25 Nov 2020 16:19:48 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 84F8F206F7 for ; Wed, 25 Nov 2020 16:19:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="PTfQBiuT"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="1ayJQZhc" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 84F8F206F7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:Mime-Version:References:In-Reply-To:Message-Id: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=kYGsuWjFuLNXG7H+E+M9NewKjGlffzfm3LN0N7x4EoA=; b=PTfQBiuTs47Gjo6ox7VWqBcZd BMS+l3e9/H/XydQ6F3KlnGkxj7DF8DW5XonchqyFVtp+HKRpzsjf0cEvwh5FFFNPRyj4YcDi8giL6 Yqon/ky6w6W4a6ijYlJWY3G7AF4+mAU9KAG9o+x/6NKLWeQ26+UVOQRTaBaHSsGggRCNvGrsk8PV7 SB69u0UfbCDNaw7PcNf3Bf19uQQL2+3hoS45133CzJ2eHG3T3GfBCb76Ky6tqKuL8fu9zg1dTynXk ZfLVE0QviNndKeYJm1J5yxqx7I+EvO8UaZWccnaShsGUYWwSRR9CfQdYJd+9TvonPFsiCRJ8u6xtg 1ZKrdjSFQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1khxUv-0008I3-RH; Wed, 25 Nov 2020 16:18:25 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1khxUt-0008He-I1 for linux-arm-kernel@lists.infradead.org; Wed, 25 Nov 2020 16:18:24 +0000 Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id BDC03206F7; Wed, 25 Nov 2020 16:18:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1606321102; bh=uiyBZtNvvHeode0AM6eJ2wMA3w8xIbX9bIPIYXMX6Xo=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=1ayJQZhct7h2cxsEh2Ftaa9axPgXN7TUynf99PaB67fA39c5tCM3vRBE4Wp/yjNtf F7SFM1yri2AOJJzi80bzjDAdgj53vgO0nR3Vov4xqIC+d4BlsHTDpAbO6eGhDKkFLR lH8ce+alNedyP1C4OU5NoIWNiEEv7YvOhEBjTLEA= Date: Thu, 26 Nov 2020 01:18:17 +0900 From: Masami Hiramatsu To: Will Deacon Subject: Re: [PATCH] arm64: Fix early single-stepping Message-Id: <20201126011817.9804ca51853636af4364858b@kernel.org> In-Reply-To: <20201125161133.GA16924@willie-the-truck> References: <20201026172907.1468294-1-jean-philippe@linaro.org> <20201027191318.aba935f7ccf00af9acd89388@kernel.org> <20201027194258.43b157ac0bbccd918fc8756a@kernel.org> <20201027115909.GB1514990@myrica> <20201027123317.GA26351@willie-the-truck> <20201027224922.7b032857d53bbfdc4484f768@kernel.org> <20201028082820.GA2328726@myrica> <20201028083643.GA27678@willie-the-truck> <20201126010906.dd56ca668e30de6be9380028@kernel.org> <20201125161133.GA16924@willie-the-truck> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201125_111824_030416_A5867F8D X-CRM114-Status: GOOD ( 26.02 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jean-Philippe Brucker , Steven Rostedt , dianders@chromium.org, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, 25 Nov 2020 16:11:34 +0000 Will Deacon wrote: > Hi Masami, > > On Thu, Nov 26, 2020 at 01:09:06AM +0900, Masami Hiramatsu wrote: > > On Wed, 28 Oct 2020 08:36:44 +0000 > > Will Deacon wrote: > > > Cheers. An alternative (which I think would be better in the long run > > > anyway) would be to avoid using hardware step in kprobes and instead rely > > > on a BRK instruction to trap after running the trampoline. > > > > We started working on using the BRK instead of hardware step in kprobes > > in other threads. However, there still be a bug in the kernel. > > I would like to fix or at least mitigate this issue until this is released > > (since it's a bug) > > > > Would you think we can push the BRK only kprobes until it or in stable kernel? > > Or, we should add a mitigation patch for this bug? > > For the mitigation, I think we can introduce a kconfig flag which indicates > > the arch doesn't support early kprobes, in that case we defer the kprobe and > > boot-time trace later stage. This flag will be removed after we introduce the > > BRK-only kprobes. > > The BRK stuff is merged upstream: > > http://git.kernel.org/linus/7ee31a3aa8f49 > > Are you saying that this isn't sufficient to fix the problem? Oops, No, it should be enough. I thought we were still in discussion on the other thread... Anyway, thank you for merging! -- Masami Hiramatsu _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel